Stylesheets

A stylesheet is a named CSS block a template version can point at. Keeping it separate from the markup means one house style can back every template you have, and correcting a button colour is one edit rather than one per localization.

Why it is inlined rather than linked

Mail clients are not browsers. Gmail’s web client strips a <style> block, Outlook does the same, and nothing loads an external stylesheet at all. So at render time the rules are resolved against the document and written onto the elements they matched, as style attributes — which is the only form of CSS that survives the trip reliably.

Two things follow from that:

• Class names are kept. Inlining does not strip them, so the delivered markup stays readable and anything that has to find an element by class still can.
• Selectors that cannot be resolved statically do nothing. A rule keyed on :hover, a media query, or a pseudo-element has no element to write itself onto, so it stays in the block and reaches only the clients that read one. Write the layout with attributes and inline-able rules, and treat the rest as progressive enhancement.

If inlining fails outright, or the stylesheet and the markup together are too large to inline in bounded time, the message still goes out with the <style> block intact. That is worse styling in some clients, which beats a failed send on a path where refusing costs somebody their mail.

Create

POST /api/v1/stylesheets

name is required, css is optional and capped at 256 KB.

curl -X POST http://localhost:3000/api/v1/stylesheets \
  -H "Authorization: Bearer myk_..." \
  -H "Content-Type: application/json" \
  -d '{
    "name": "house",
    "css": "h1 { font: 600 22px/1.3 Helvetica, Arial, sans-serif; color: #1a1a1a } .btn { display: inline-block; padding: 12px 24px; background: #6d28d9; color: #fff; border-radius: 6px; text-decoration: none }"
  }'

List

GET /api/v1/stylesheets

Read one

GET /api/v1/stylesheets/{id}

Replace

PUT /api/v1/stylesheets/{id}

A full replace, not a patch — name is required on every call, and omitting css empties it.

Delete

DELETE /api/v1/stylesheets/{id}

Returns 204. A version still pointing at the deleted sheet is not broken by this: it renders unstyled rather than failing, on the same reasoning as the inlining fallback above. Watch for it in a preview, since nothing raises an error.

Attaching one

A stylesheet applies through the version, not the template:

PATCH /api/v1/templates/{templateId}/versions/{versionId}
{ "stylesheet_id": "0198f6a1-3c7e-7b21-9f4d-2a5c8e0b1d33" }

The stylesheet itself is shared and live: PUT /api/v1/stylesheets/{id} changes the CSS of every version pointing at it, the active ones included, from the next send on. That is what makes a house-style correction one edit. To restyle through review instead, create a new stylesheet, point a draft version at it, preview, and activate that version - the live version keeps the old sheet until then.